Mango leaves are the leaves of Mangifera Indica L. In traditional Chinese medicine, mango is considered as having sweet and sour taste, mild as a medicine, non-poisonous, which can reach liver channel and spleen channel and is advantageous to stomach. Its action includes generating saliva, quenching thirst, preventing vomiting, promoting urination. It is suitable for treating the conditions such as thirst, dryness of the throat, insufficiency of the stomach property (stomach-qi), vertigo, and vomiting. According to Diet Herbal (Shi Xing Ben Cao), mango can treat the conditions such as channel obstruction (Jing Mai Bu Tong) in females. Supplement to Compendium of Materia Medica (Ben Cao Gang Mu Shi Yi) recorded that mango can prevent sealers from having seasickness after sealers eat mango and that mango can prevent vomiting because it is advantageous to the stomach property. The applications of mango leaves as medicine was first recorded in Lingnan Cai Yao Record (Ling Nan Cai Yao Lu). Luchuan Materia Medica (Lu Chuan Ben Cao), Nanning Medicine Magazine (Nanning Shi Yao Wu Zhi) (First Edition, 1959) and The National Assembly of Chinese Herbal Medicine (Quan Guo Zhong Cao Yao Hui Bian) also stated the applications of mango leaves as medicine under the item of mango. Mango leaves were first stated as a Chinese medicine alone in the Dictionary of Chinese Medicine (Zhong Yao Da Ci Dian) published in 1977. As stated in Standards for Chinese Medicine in Guangxi (Guangxi Zhong Yao Cai Biao Zhun), mango leaves are recorded as tasting sour, sweet, cool and mild, having the function of promoting the circulation of properties (qi), dispersing stagnancy and dispelling measles, which can be used to treat the conditions such as stomachache, property (qi) distension, infantile malnutritional stagnation, thirst and so forth. In China, mango grows in Taiwan, Guangdong, Guangxi, Hainan, Fujian, Yunnan and Sichuan provinces and has a plenty of resources.
The chemical components of mango leaves include ascorbic acid, tannin, mangiferin, ellagic acid, catechol, shikimic acid, quinic acid, kaempferol, thujene and so forth. The prior pharmacology studies indicate that the extracts from mango leaves have functions such as preventing asthma, relieving cough, and eliminating sputum. In 1973, mango leaves were developed into a medicine named Mango Tablets for Relieving Cough by Guangxi College of Chinese Medical and the medicine was approved as one of the National Protected Chinese Medicines in 1998 and was approved as one of the National Essential Medicines in the same year. The typical component in mango leaves is mangiferin, which has the effects such as anti-lipid peroxidation, immunization, Anti-inflammation, Analgesia, liver protection and cholagogue, antivirus, antitumor, central nervous system excitation and so forth.
α-glucosidase exists on the brush border of human intestine and participates the metabolization of saccharides in human body, which play an important role in maintaining the normal physiological functions of human. α-glucosidase cut off glucose from the non-reducing ends of starch and polysaccharide by hydrolyzing α-1,4 glucoside bonds. The absorption of carbohydrates such as starch, dextrin, sucrose, etc. in human body depends on the activity of α-glucosidase. α-glucosidase inhibitor is a medicine used for treating diabetes clinically, which currently obtained from metabolites of microorganism, such as acarbose (tradename: Glucobay), voglibose (tradename: Basen), miglitol, and so forth. Clinical application has proved that acarbose, voglibose and so forth are good medicines for treating diabetes because they have prominent effects of decreasing the Postprandial hyperglycemia for treating type II diabetes. It can be seen that α-glucosidase inhibitors can effectively suppress the activity of α-glucosidase on the brush border of intestine wall so that the degradation of carbohydrates and the adsorption rate of carbohydrates in the alimentary canal are deferred and hindered. Therefore, the glucose absorption derived from disaccharides, oligosaccharides and polysaccharides is deferred, and the time and progress of blood glucose increase in patients are effectively deferred, so α-glucosidase inhibitors are helpful to control the blood glucose increase of type II diabetes.
However, there is still a need for new methods for treating diabetes, for example, type II diabetes. A new research field at present is to look for α-glucosidase inhibitors with high safety from natural products to decrease blood glucose.